Method of inhibiting production of projections in metal deposited-film

ABSTRACT

A method of inhibiting production of projections in a metal deposited-film according to the present invention is characterized by using a vapor deposition apparatus comprising, in a vacuum-treating chamber, an evaporating section for a depositing material, and an accommodating member and/or a holding member for accommodation and/or hold of work pieces, respectively, and, in depositing a metal depositing material on each of the surface of the work pieces with the accommodating member and/or the holding member being made rotated about the horizontal rotational axis thereof, carrying out vapor deposition with a Vickers hardness of a film formed on each of the surface of the work pieces maintained at 25 or more. According to the present invention, production of projections in a metal deposited-film can be effectively inhibited when forming the metal deposited-film of aluminum, zinc or the like on the surface of a work piece such as a rare earth metal-based permanent magnet.

TECHNICAL FIELD

[0001] The present invention relates to a method of inhibitingproduction of projections in a metal deposited-film when forming themetal deposited-film of aluminum, zinc or the like on the surface of awork piece such as a rare earth metal-based permanent magnet.

BACKGROUND OF THE INVENTION

[0002] A rare earth metal-based permanent magnet such as an R—Fe—B basedpermanent magnet, of which an Nd—Fe—B based permanent magnet isrepresentative, is used at present in a variety of fields, because ithas a high magnetic characteristic.

[0003] However, the rare earth metal-based permanent magnet containsmetal species (in particular, R) liable to be corroded by oxidation inthe atmosphere. Therefore, when the rare earth metal-based permanentmagnet is used without being subjected to a surface treatment, thecorrosion of the magnet is advanced from its surface due to theinfluence of a small amount of acid, alkali and/or water to producerust, thereby bringing about the deterioration and dispersion of themagnetic characteristic. Further, when the magnet having the rustproduced therein is incorporated into a device such as a magneticcircuit, there is a possibility that the rust is scattered to pollutesurrounding parts or components.

[0004] With the foregoing in view, it is a conventional practice to forma metal deposited-film of aluminum, zinc or the like on the surface of arare earth metal-based permanent magnet for the purpose of providing anexcellent corrosion resistance to the rare earth metal-based permanentmagnet.

[0005] In particular, an aluminum film is, in addition to beingexcellent in corrosion resistance and mass productivity, excellent inreliability of adhesion with an adhesive required in assembling parts (apeel-off is difficult to occur between the film and the adhesive beforereaching an intrinsic fracture strength of the adhesive). Thus, thealuminum film is widely applied to rare earth metal-based permanentmagnets for which strong adhesive strength is required. As the adhesivehere, in compliance with purposes of being heat resistant, impactresistant and the like, there are selected and used various kinds ofadhesives as appropriate. They are various kinds of resin adhesives suchas those of epoxy resin, phenol resin, reactive acrylic resin, modifiedacrylic resin (ultraviolet curing adhesives and anaerobic adhesives),cyanoacrylate resin, silicone resin, polyisocyanate, vinyl acetateresin, methacrylate resin, polyamide, and polyether, emulsion adhesivesof various kinds of resin adhesives (for example, vinyl acetate resinadhesives, acrylic resin adhesives and the like), various kinds ofrubber adhesives (for example, nitrite rubber adhesives, polyurethanerubber adhesives and the like), and ceramic adhesives.

[0006] Examples of apparatus used for forming a metal deposited-film onthe surface of a rare earth metal-based permanent magnet, include anapparatus described in U.S. Pat. No. 4,116,161 and an apparatusdescribed in Graham Legge, “Ion Vapor Deposited Coatings for ImprovedCorrosion Protection”: Reprinted from Industrial Heating, September,135-140, 1994. FIG. 1 is a diagrammatic front view (a partiallyperspective view) of the inside of a vacuum-treating chamber 1 connectedto an evacuating system (not shown) in one example of such apparatus.Two cylindrical barrels 5, for example, formed of a mesh net of astainless steel are disposed side-by-side in an upper area in thechamber for rotation about a rotary shaft 6 on a horizontal rotationalaxis. A plurality of boats 2, which are evaporating sections forevaporating, for example, aluminum as a metal depositing material, aredisposed on a boat support base 4 risen on a support table 3 in a lowerarea in the chamber.

[0007] With this apparatus, a plurality of rare earth metal-basedpermanent magnets 30 as work pieces are placed into each of thecylindrical barrels 5, and aluminum is evaporated from the boats 2heated to a predetermined temperature by a heating means (not shown),while rotating the cylindrical barrels about the rotary shaft 6, asshown by an arrow, thereby forming a deposited-film of aluminum on thesurface of each of the rare earth metal-based permanent magnets 30 inthe cylindrical barrels 5.

[0008] The vapor deposition apparatus shown in FIG. 1 is capable oftreating a large amount of the work pieces and excellent inproductivity. However, projections might have been produced in somecases on the metal deposited-film formed on the surface of each of therare earth metal-based permanent magnets.

[0009] Presence of such projections in the film adversely affectsadhesion of the magnets when assembling the magnets onto parts by usingadhesive. In particular, for the projections exceeding a mean line ofroughness curves (phase correct filtered mean line) according to JISB0601-1994 by 100 μm or more, the adhesive has to be applied with aconsiderably large thickness so as to avoid the influence of thepresence of the projections for ensuring sufficient adhesion. Therefore,use of an adhesive with low viscosity can not ensure to provide such athickness with resulting insufficient adhesion. Moreover, use of anadhesive such as a cyanoacrylate adhesive that is cured through achemical reaction with the surface of the film provides insufficientcuring, which results in obtaining insufficient adhesion. Furthermore,even in the case where no adhesive is used as in an interior permanentmagnet (IPM) type motor, presence of the projections prevents parts frombeing provided with high dimensional accuracy with resulting difficultyin complying with recent requirements of the parts for being reduced insize and provided with high-accuracy.

[0010] Accordingly, it is an object of the present invention to providea method of effectively inhibiting production of projections in a metaldeposited-film of aluminum, zinc or the like when forming the metaldeposited-film on the surface of a work piece such as a rare earthmetal-based permanent magnet.

DISCLOSURE OF THE INVENTION

[0011] The inventors have carried out detailed studies with analysesabout why and how the projections are produced in the metaldeposited-film and, as a result, have found the following facts. Namely,in the vapor deposition apparatus as shown in FIG. 1, the rotation ofthe cylindrical barrel in thus constituted apparatus causes in thebarrel such phenomena as collisions and rubbings of the rare earthmetal-based magnets accommodated in the barrel against one another.Moreover, there are caused phenomena of collisions and rubbings betweenthe magnets and the barrel wall. This damages the metal deposited-filmformed on each of the magnets to be partially shaved off. The shaved offfragments further rub against the magnets and the like to be granulatedand adhere on other film portions, on which films are further formed.Thus, projections are produced which can not be removed by such peeningwork (cf. JP-A-62-60212) as to be usually carried out after filmformation with a purpose of improving corrosion resistance of the film.Furthermore, the magnets are always in a state of being heated by aradiant heat from the evaporating section. Thus, the metaldeposited-film formed on the surface of each of the magnets has beensoftened by a rise in temperature more than necessary to be easilydamaged.

[0012] The present invention has been accomplished on the basis of theabove findings, and a method of inhibiting production of projections ina metal deposited-film according to the present invention is, as claimedin claim 1, characterized by using a vapor deposition apparatuscomprising, in a vacuum-treating chamber, an evaporating section for adepositing material, and an accommodating member and/or a holding memberfor accommodation and/or hold of work pieces, respectively, and, indepositing a metal depositing material on each of the surface of thework pieces with the accommodating member and/or the holding memberbeing made rotated about the horizontal rotational axis thereof,carrying out vapor deposition with a Vickers hardness of a film formedon each of the surface of the work pieces maintained at 25 or more.

[0013] According to a method as claimed in claim 2, in the methodaccording to claim 1, it is characterized in that a temperature of eachof the work pieces accommodated and/or held in the accommodating memberand/or the holding member, respectively, is maintained at ⅔ or less amelting point in bulk (Tm) (°C.) of the metal depositing material tothereby maintain the Vickers hardness of the film formed on each of thesurface of the work pieces at 25 or more.

[0014] According to a method as claimed in claim 3, in the methodaccording to claim 2, it is characterized in that the metal depositingmaterial is aluminum, with which vapor deposition is carried out with atemperature of the work piece maintained at 350° C. or less.

[0015] According to a method as claimed in claim 4, in the methodaccording to claim 2, it is characterized in that the metal depositingmaterial is zinc, with which vapor deposition is carried out with atemperature of the work piece maintained at 250° C. or less.

[0016] According to a method as claimed in claim 5, in the methodaccording to any one of claim 1 to claim 4, it is characterized in thatthe vapor deposition is carried out by a vacuum evaporation process oran ion plating process.

[0017] According to a method as claimed in claim 6, in the methodaccording to any one of claim 1 to claim 5, it is characterized in thatthe accommodating member and/or the holding member are/is detachablyconstituted.

[0018] According to a method as claimed in claim 7, in the methodaccording to any one of claim 1 to claim 6, it is characterized in thatthe accommodating member is a tubular barrel formed of a mesh net.

[0019] According to a method as claimed in claim 8, in the methodaccording to claim 7, it is characterized in that the tubular barrel isrevolvably supported circumferentially outside a horizontal rotationalaxis of a support member made rotatable about the rotational axis, forrevolution about the rotational axis of the support member by rotatingthe support member.

[0020] According to a method as claimed in claim 9, in the methodaccording to claim 8, it is characterized in that the tubular barreland/or the support member supporting the tubular barrel are/isdetachably constituted.

[0021] According to a method as claimed in claim 10, in the methodaccording to claim 8, it is characterized in that a plurality of thetubular barrels are supported in an annular shape circumferentiallyoutside the rotational axis of the support member.

[0022] According to a method as claimed in claim 11, in the methodaccording to claim 7, it is characterized in that the inside of thetubular barrel is divided to form two or more accommodating sections.

[0023] According to a method as claimed in claim 12, in the methodaccording to claim 11, it is characterized in that the inside of thetubular barrel is divided radially from a rotational axis to form two ormore accommodating sections.

[0024] According to a method as claimed in claim 13, in the methodaccording to any one of claim 1 to claim 12, it is characterized in thatthe work piece is a rare earth metal-based permanent magnet.

[0025] In addition, a rare earth metal-based permanent magnet accordingto the present invention is, as claimed in claim 14, characterized byhaving a metal deposited-film in which production of projections isinhibited by the method according to claim 13.

[0026] According to a rare earth metal-based permanent magnet as claimedin claim 15, in the rare earth metal-based permanent magnet according toclaim 14, it is characterized in that a height of the projection existsin the metal deposited-film is above a mean line of roughness curves(phase correct filtered mean line) according to JIS B0601-1994 by 100 μmor less.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a diagrammatic front view (a partially perspective view)of the inside of a vacuum-treating chamber in one example of a vapordeposition apparatus applied to the present invention;

[0028]FIG. 2 is a diagrammatic front view (a partially perspective view)of the inside of a vacuum-treating chamber in another example of a vapordeposition apparatus applied to the present invention;

[0029]FIG. 3 is a diagrammatic perspective view of cylindrical barrelssupported on support members thereof;

[0030]FIG. 4 is a diagrammatic front view (a partially perspective view)of the inside of a vacuum-treating chamber in further another example ofa vapor deposition apparatus applied to the present invention;

[0031]FIG. 5 is a diagrammatic perspective view of the cylindricalbarrel whose inside is divided; and

[0032]FIG. 6 is a diagrammatic perspective view of a jig used for thefurther another example of a vapor deposition apparatus applied to thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0033] A method of inhibiting production of projections in a metaldeposited-film according to the present invention is characterized byusing a vapor deposition apparatus comprising, in a vacuum-treatingchamber, an evaporating section for a depositing material, and anaccommodating member and/or a holding member for accommodation and/orhold of work pieces, respectively, and, in depositing a metal depositingmaterial on each of the surface of the work pieces with theaccommodating member and/or the holding member being made rotated aboutthe horizontal rotational axis thereof, carrying out vapor depositionwith a Vickers hardness of a film formed on each of the surface of thework pieces maintained at 25 or more.

[0034] Namely, the present invention is based on the following finding.According to the finding, vapor deposition, carried out whilesuppressing a more than necessary temperature rise of the work pieces,allows a Vickers hardness of a film formed on each of the surface of thework pieces to be maintained at 25 or more. This inhibits the film frombeing softened to become damageable by collisions and rubbings of thework pieces against one another and by collisions and rubbings betweenthe work pieces and the barrel wall. As a result, production ofprojections in the film can be effectively inhibited.

[0035] The work pieces each being as a target of forming the metaldeposited-film in the present invention are not necessarily limited toparticular ones if the metal deposited-film can be formed thereon. Thepresent invention, however, particularly exhibits the effect thereof forthe rare earth metal-based magnets for which strong adhesive strength toan adhesive is required when assembled onto parts because of the strongmagnetic force thereof.

[0036] Metal depositing material utilized in the present invention isnot limited to particular one. The present invention, however, exhibitsthe effect thereof when particularly applied to aluminum, zinc, tin,lead, bismuth, or an alloy containing at least one of these metalcomponents. Each of them has a low melting point such that thedeposited-film is liable to soften by a temperature rise of the workpiece.

[0037] In the present invention, in order to carry out vapor depositionwith a Vickers hardness of a film formed on each of the surface of thework pieces maintained at 25 or more, it is necessary only that thevapor deposition is carried out with the temperature of each of the workpieces accommodated or held in the accommodating member or the holdingmember, respectively, being maintained at ⅔ or less a melting point inbulk (Tm) (°C.) of the metal depositing material. The melting points inbulk of the above metal depositing materials are 660° C., 420° C., 232°C., 328° C., and 271° C. for aluminum, zinc, tin, lead, and bismuth,respectively. In an alloy, when there exists a coexistence state of twophases of a solid phase and a liquid phase at a high temperature, atemperature corresponding to a composition on a solid us is taken as amelting point. When the work piece is a rare earth metal-based permanentmagnet, aluminum or zinc is preferable as the metal depositing materialwith consideration of cost. In using aluminum, vapor deposition is wellcarried out with a temperature of the magnet maintained at ⅔ or less amelting point in bulk of aluminum, namely, 440° C. or less. It is,however, preferable to carry out the vapor deposition with thetemperature maintained at 350° C. or less, and more preferable to carryout the vapor deposition with the temperature maintained at 300° C. orless. When zinc is used, vapor deposition is well carried out with atemperature of the magnet maintained at ⅔ or less a melting point inbulk of zinc, namely, 280° C. or less. It is, however, preferable tocarry out the vapor deposition with the temperature maintained at 250°C. or less.

[0038] A lower limit of the temperature of the work piece is, for thework piece being the rare earth metal-based permanent magnet, generallytaken as being at 100° C. This is because a vapor deposition carried outat a temperature lower than 100° C. provides a possibility of achievingno sufficient adhesion between the magnet and the metal deposited-film.

[0039] The method of inhibiting production of projections in a metaldeposited-film according to the present invention is suitably applied tovapor deposition processes such as a vacuum evaporation process, an ionplating process, a beam process, and a CVD process. Namely, in each ofsuch processes, the temperature of the work piece might have risen morethan necessary at the vapor deposition to cause resulting production ofprojections in the film. Of these processes, a vapor deposition processwith a resistance heating system as is adopted in the vacuum evaporationprocess or the ion plating process, particularly a vapor depositionprocess with a system of continuously supplying depositing material toan electrically heated evaporating section to melt it, can carry outdeposition with a high deposition rate and is useful for treating alarge amount of the work pieces. Therefore, by applying the method ofinhibiting production of projections in a metal deposited-film accordingto the present invention to such a vapor deposition process, an effectis exhibited with which a film with excellent quality can be formed oneach of the surface of the work pieces efficiently as well as stably.

[0040] A vapor deposition apparatus applied to the present invention isan apparatus which comprises, in a vacuum-treating chamber, anevaporating section for a depositing material and an accommodatingmember for accommodation of work pieces, and can deposit a depositingmaterial on each of the surface of the work pieces with theaccommodating member being made rotated about the horizontal rotationalaxis thereof. As an example of such an apparatus, there can be presentedthe following ones.

[0041] For example, there is presented a vapor deposition apparatus asshown in the above FIG. 1. In using such an apparatus, for a method ofcarrying out the vapor deposition with a Vickers hardness of a filmformed on each of the surface of the work pieces maintained at 25 ormore, there is a method of completing the vapor deposition before atemperature of each of the accommodated work pieces reaches ⅔ a meltingpoint in bulk (Tm)(°C.) of the metal depositing material, a method oftemporarily discontinuing the vapor deposition before the temperaturereaches ⅔ the melting point, cooling the work pieces before resuming thevapor deposition and repeating the process, a method of maintaining thetemperature of each of the work pieces below ⅔ the melting point byintroducing into a cylindrical barrel a cooling mechanism using coolingwater, cooling gas or the like, a method of disposing a shielding platefor reducing a radiant heat from the evaporating section, or the like.

[0042] In addition, the use of the vapor deposition apparatus as shownin FIG. 2 can effectively suppress more than necessary temperature riseof the work pieces to allow the vapor deposition to be easily carriedout with a Vickers hardness of a film formed on each of the surface ofthe work pieces maintained at 25 or more.

[0043]FIG. 2 is a diagrammatic front view (a partially perspective view)of the inside of a vacuum-treating chamber 51 connected to an evacuatingsystem not shown (description will be made with an apparatus for forminga deposited-film of aluminum on the surface of each of rare earthmetal-based permanent magnets taken as an example).

[0044] In an upper area in the chamber, two support members 57 maderotatable about a rotary shaft 56 on a horizontal rotational axis aredisposed side-by-side. Circumferentially outside the rotary shaft 56 ofthe support member 57, six cylindrical barrels 55 formed of, forexample, a mesh net of a stainless steel are supported in an annularshape by support shafts 58 revolvably about the rotary shaft 56. In alower area in the chamber, a plurality of boats 52, which areevaporating sections for evaporating a metal depositing material, aredisposed on a boat support base 54 risen on a support table 53.

[0045] Inside below the support table 53, an aluminum wire 59, which isa metal depositing material, is retained and wound around a feed reel60. A proceeding end of the aluminum wire 59 is guided to above the boat52 by a thermal resistant protective tube 61 made to face toward aninner surface of the boat 52. A cut out window 62 is provided in aportion of the protective tube 61, and feeding gears 63 are mounted incorrespondence to the cut out window 62 to come into direct contact withthe aluminum wire 59. Thus, a constitution is provided so that aluminumis constantly supplied into the boat 52 by feeding the aluminum wire 59.

[0046]FIG. 3 is a diagrammatic perspective view showing that the sixcylindrical barrels 55, each formed of the mesh net of the stainlesssteel, are supported revolvably in the annular shape by the supportshaft 58 circumferentially outside the rotary shaft 56 of the supportmember 57 that is made rotatable about the rotary shaft 56 on thehorizontal rotational axis (the cylindrical barrels are supported intandem and hence, the total number of the cylindrical barrels supportedis twelve) (magnets are not accommodated yet).

[0047] When the support member 57 is rotated about the rotary shaft 56(see an arrow in FIG. 2), the cylindrical barrel 55 supported by thesupport shaft 58 circumferentially outside the rotary shaft 56 of thesupport member 57 is made revolve about the rotary shaft 56 in responseto the rotation of the support member 57. As a result, the distancebetween the individual barrel and the evaporating section disposed belowthe support member is to be Varied, whereby the following effect isexhibited.

[0048] Namely, the cylindrical barrel located at a lower portion of thesupport member 57 is close to the evaporating section. Therefore, ametal deposited-film is efficiently formed on a surface of each of rareearth metal-based permanent magnets 80 accommodated in this cylindricalbarrel. On the other hand, a temperature rise in each of rare earthmetal-based permanent magnets accommodated in the cylindrical barrelmoved away from the evaporating section is reduced by an amountcorresponding to a distance away from the evaporating section.Therefore, during this time, the softening of a metal deposited-film isinhibited which is formed on a surface of each of the magnets. In thisway, the use of this vapor deposition apparatus makes it possible tosimultaneously achieve the efficient formation of the metaldeposited-film and the inhibition of the softening of the formed metaldeposited-film, which can effectively inhibit production of projections.

[0049] The vapor deposition apparatus is convenient in that it exhibitsthe above-described effect and, along with this, has followingadvantages.

[0050] Namely, even when a mass treatment is carried out, a treatment inthis vapor deposition apparatus, carried out with a small amount ofmagnets accommodated in each of the cylindrical barrels, can reduce thefrequency of collision and rubbing of the magnets against one anotherwithin the barrel rather than the treatment with a larger amount ofmagnets accommodated in a single cylindrical barrel as in the vapordeposition apparatus shown in FIG. 1. Hence, it becomes possible tofurther inhibit the production of projections caused by damaged films.

[0051] When accommodated in a cylindrical barrel having a large R(radius of curvature) in the vapor deposition apparatus as shown in FIG.1 for vapor deposition treatment, magnets like bow-shaped or large-sizedones slip down along the inner surface of the barrel and are liable todamage the films due to rubbing against the inner surface of the barrel.Even for such magnets, by accommodating them in each of the cylindricalbarrels having a smaller radius R in this vapor deposition apparatus forvapor deposition treatment, it becomes possible to stir the magnetsuniformly to permit further inhibiting production of projections due todamaged films.

[0052] Previously, for the purpose of the reduction of the frequency ofcollision and that of rubbing of the magnets against one another withinthe barrel, a method of using dummies (e.g., there are presented ceramicballs having a diameter of 10 mm), which were sometimes accommodated inthe barrel along with magnets, was adopted in some cases. However, theuse of this vapor deposition apparatus eliminates the need for using thedummies to make it possible to enhance the efficiency of the formationof films on the magnets. This facilitates the vapor deposition to becompleted before the temperature of the magnets reaches ⅔ the meltingpoint in bulk (Tm)(°C.) of the metal depositing material.

[0053] In the vapor deposition apparatus shown in FIG. 2 and FIG. 3, thesupport member 57 for supporting the cylindrical barrel 55 is disposedin the upper area in the vacuum-treating chamber 51. The boat 52, whichis the evaporating section, is disposed in the lower area in the chamber51. Nevertheless, the positional relationship between the support memberand the evaporating section is not limited to the above relationship.The support member and the evaporating section may be disposed at anylocations in the vacuum-treating chamber if they are in a positionalrelationship ensuring that the distance between the cylindrical barreland the evaporating section can be varied by rotating the supportmember. However, the evaporating section being disposed outside thesupport member allows the distance between the support member and theevaporating section to be set in a wide range within the internal spacein the vacuum-treating chamber. Therefore, it becomes possible to easilyset a distance desirable for efficiently forming a metal deposited-filmand inhibiting the softening of the formed film. In addition, even whena deposited-film is formed while the metal depositing material beingmolten and evaporated, arrangement of each of the members or componentscan be easily determined for becoming excellent also in handling.

[0054] In addition, in the vapor deposition apparatus shown in FIG. 2and FIG. 3, the six cylindrical barrels 55 are supported on one surfaceof one of the support members 57 (the cylindrical barrels are supportedin tandem and hence, the total number of the cylindrical barrelssupported is twelve). However, the number of the cylindrical barrelssupported on one of the support members is not limited to six and may beone.

[0055] The cylindrical barrel 55 may be supported so that it revolvesabout the rotary shaft 56 of the support member 57 and, along with this,rotates itself about the support shaft 58 by a known mechanism.

[0056] In addition, also the use of the vapor deposition apparatus asshown in FIG. 4 can effectively suppress more than necessary temperaturerise of the work pieces to allow the vapor deposition to be easilycarried out with a Vickers hardness of a film formed on each of thesurface of the work pieces maintained at 25 or more.

[0057]FIG. 4 is a diagrammatic front view (a partially perspective view)of the inside of a vacuum-treating chamber 101 connected to anevacuating system not shown (description will be made with an apparatusfor forming a deposited-film of aluminum on the surface of each of rareearth metal-based permanent magnets taken as an example).

[0058] In an upper area in the chamber, there are disposed side-by-sidetwo cylindrical barrels 105 formed of, for example, a mesh net of astainless steel and made rotatable about a rotary shaft 106 on ahorizontal rotational axis. The inside of the cylindrical barrel 105 isdivided radially from a rotational axis into six to form accommodatingsections each being sector-shaped in section. In a lower area in thechamber, a plurality of boats 102, which are evaporating sections forevaporating a metal depositing material, are disposed on a boat supportbase 104 risen on a support table 103.

[0059] Inside below the support table 103, an aluminum wire 109, whichis a metal depositing material, is retained and wound around a feed reel110. A proceeding end of the aluminum wire 109 is guided to above theboat 102 by a thermal resistant protective tube 111 made to face towardan inner surface of the boat 102. A cut out window 112 is provided in aportion of the protective tube 111, and feeding gears 113 are mounted incorrespondence to the cut out window 112 to come into direct contactwith the aluminum wire 109. Thus, a constitution is provided so thataluminum is constantly supplied into the boat 102 by feeding thealuminum wire 109.

[0060]FIG. 5 is a diagrammatic perspective view showing the cylindricalbarrel 105 formed of the mesh net of the stainless steel, rotatableabout the rotary shaft 106 on the horizontal rotational axis, and havingthe inside divided radially from the rotational axis into six to formthe accommodating sections each being sector-shaped in section (magnetsare not accommodated yet).

[0061] When the cylindrical barrel 105 is rotated about the rotary shaft106 (see an arrow in FIG. 4), the distance between the individualaccommodating section defined in the cylindrical barrel and theevaporating section disposed below the accommodating sections is to bevaried. Thus, like in the case where the vapor deposition carried out byusing the vapor deposition apparatus shown in FIG. 2 and FIG. 3,production of projections can be effectively inhibited.

[0062] In the vapor deposition apparatus shown in FIG. 4 and FIG. 5, inthe upper area in the vacuum-treating chamber 101, there is disposed thecylindrical barrel 105 whose inside is divided radially from therotational axis into six to form the accommodating sections each beingsector-shaped in section. In the lower area in the chamber 101, there isdisposed the boat 102 which is the evaporating section. However, thepositional relationship between the cylindrical barrel and theevaporating section is not limited to the above relationship. Thecylindrical barrel and the evaporating section may be disposed at anylocations in the vacuum-treating chamber if they are in a positionalrelationship ensuring that the distance between the accommodatingsection and the evaporating section can be made freely variable byrotating the cylindrical barrel.

[0063] Moreover, in the vapor deposition apparatus shown in FIG. 4 andFIG. 5, the inside of the cylindrical barrel is divided radially fromthe rotational axis into six to form the accommodating sections eachbeing sector-shaped in section. However, the accommodating sectionsformed in the cylindrical barrel may be defined by any divided form ifthe form ensures that the distance between the accommodating section andthe evaporating section can be made freely variable by rotating thecylindrical barrel.

[0064] The shape of the barrel as an accommodating member in any of theabove described vapor deposition apparatuses is not limited to becylindrical, but may be polygonal-prism-shaped with the section formedin hexagonal, octagonal, or the like, if it is tubular.

[0065] As the mesh, there can be presented mesh nets made of stainlesssteel and titanium. The reason why the stainless steel and titanium aredesirable as materials for the mesh net is that the materials areexcellent in strength and in durability to etching agents or releasingagents such as alkaline aqueous solutions used in an operation forremoving the depositing material deposited on the barrel. The mesh maybe made using a net-shaped plate produced by punching or etching a flatplate, or may be made by knitting a linear material.

[0066] The open area ratio of the mesh (a ratio of the area of openingsto the area of the mesh) depends on the shape and the size of a workpiece. For improving an efficiency of forming films onto the work piecesand for easily completing the vapor deposition before the temperature ofeach of the work pieces reaches ⅔ the melting point in bulk (Tm)(°C.) ofthe metal depositing material, the ratio is desirably taken as being 50%or more, more desirably as being 60% or more. Although the upper limitof the open area ratio is not particularly limited, for the open arearatio being more than 95%, there is a possibility that the mesh isdeformed or damaged in the vapor deposition treatment or in other kindsof handling. Therefore, the ratio is desirably taken as being 95% orless, more desirably as being 85% or less. In addition, the wirediameter of the mesh is selected in consideration of the open area ratioand the strength thereof, and is, in general, desirably in a range of0.1 mm to 10 mm. Further, with easiness in handling taken intoconsideration, the wire diameter of the mesh is more desirably in arange of 0.3 mm to 5 mm.

[0067] The vapor deposition apparatus applied to the present inventionis an apparatus which comprises, in a vacuum-treating chamber, anevaporating section for a depositing material and a holding member forhold of work pieces, and can deposit a depositing material on each ofthe surface of the work pieces with the holding member being maderotated about the horizontal rotational axis thereof. As an example ofsuch an apparatus, there can be presented one in which a jig shown inFIG. 6 is used instead of the cylindrical barrel in the apparatus shownin FIG. 1. Namely, there can be presented an apparatus in which hangermembers 160 are revolvably supported circumferentially outside therotary shaft 156 of the support member 157 that is made rotatable aboutthe rotary shaft 156 on the horizontal rotational axis. The hangermembers 160 are provided as holding members for hanging work pieces 190,each with a center opening, such as ring-shaped magnets. By rotating thesupport member 157, the hanger members 160 are made revolved about therotary shaft 156 of the support member 157. In carrying out vapordeposition by using such an apparatus, rubbing is caused between ahanger member and an inner peripheral surface as a contacting portion ofeach work piece hung on the hanger member. This damages the metaldeposited-film being formed at the rubbed portion to cause a part of thefilm to be scraped off. The scraped fragments are further rubbed againstthe hanger member to be ground to be granulated. The granulatedfragments stick onto other part of the film, on which a film is furtherdeposited to cause possible production of unremovable projections.Therefore, also in carrying out vapor deposition with such an apparatus,by carrying out the deposition with a Vickers hardness of a film formedon each of the surface of the work pieces maintained at 25 or more, theeffect of the present invention can be obtained.

[0068] In a vapor deposition apparatus as described above, to constitutethe accommodating member and the holding member as being detachable fromthe support member or to constitute the support member detachable fromthe vacuum-treating chamber provides following advantages. Namely, thismakes it possible to load and unload the work pieces at any desiredplace to improve facility of the apparatus. At the completion of onedeposition treatment, the accommodating member and the holding memberthemselves have been usually heated up to a high temperature. Whensubsequent deposition treatment is carried out with the use of theaccommodating member and the holding member as being in the above state,there is a possibility of raising the temperature of the work piecesmore than necessary. Therefore, it is desirable to have time for coolingthe accommodating member and the holding member. By detachablyconstituting the accommodating member and the holding member and bypreparing a plurality thereof in the same shape, the accommodatingmember and the holding member used in one deposition treatment can beremoved and other ones can be mounted for immediately startingsubsequent deposition treatment. Hence, it becomes possible toefficiently carry out a large amount of treatment.

[0069] In addition, in the vapor deposition apparatus as above, atreatment is carried out with the inside of the accommodating memberlongitudinally divided to form two or more accommodating sections, andwith one work piece or a small quantity of work pieces accommodated ineach accommodated section. This can inhibit occurrence of cracking andbreaking of the work pieces caused by collision of the work piecesagainst one another in the accommodating member. Thus, it becomespossible to effectively inhibit production of projections accompanied bydamages of the work pieces.

EXAMPLES

[0070] The present invention will be further described in detail bycomparison of the following examples with comparative examples. Thepresent invention, however, is not limited to such examples.

[0071] The following examples and comparative examples were carried outusing sintered magnets with dimensions of 9 mm in diameter by 3 mm inthickness having a composition of Nd₁₄Fe₇₉B₆Co₁ (hereinafter referred toas magnet test pieces) which are obtained by pulverizing a known castingot and then subjecting the resulting powder to a pressing, asintering, a heat treatment and a surface working as described in, forexample, U.S. Pat. Nos. 4,770,723 and 4,792,368.

Example 1

[0072] The following experiment was carried out using the vapordeposition apparatus shown in FIG. 1 (except that the constitution aboutthe evaporating section is the same as that of the vapor depositionapparatus shown in FIG. 2). In the apparatus, the cylindrical barrel wasmade of a stainless steel with 355 mm in diameter by 1200 mm in lengthwith 64% in open area ratio of a mesh (with each opening being a squareof 4 mm in side length and with a wire of 1 mm in diameter).

[0073] Each of the magnet test pieces was subjected to a shot blasting,whereby an oxide layer on a surface of each of the magnet test pieceswas removed which was produced by a surface working at a preceding step.The magnet test pieces from each of which the oxide layer was removedwere accommodated in two cylindrical barrels with 5000 pieces for each,i.e. 10000 pieces in total. After the vacuum-treating chamber wasevacuated down to 1×10⁻³ Pa or less, while rotating the rotary shaft at1.5 rpm, the magnet test pieces were subjected to a spattering for 20minutes under conditions of an argon (Ar) gas pressure of 1 Pa and abias voltage of −500 V, whereby the surfaces of the magnet test pieceswere cleaned. Subsequently, under conditions of an Ar gas pressure of 1Pa and a bias voltage of −100 V, an aluminum wire was heated andevaporated as a metal depositing material while being supplied with awire feeding speed of 3 g/min. The evaporated aluminum was then ionizedfor forming an aluminum deposited-film on a surface of each of themagnet test pieces by an ion plating process for 20 minutes. After beingleft for cooling, the magnet test pieces having the aluminumdeposited-film were evaluated about the following items.

[0074] (1) Temperature of the magnet test pieces at completion of vapordeposition (averaged value for n=10)

[0075] (2) Vickers hardness of the aluminum deposited-film at completionof vapor deposition (averaged value for n=3)

[0076] (3) Thickness of the formed aluminum deposited-film (averagedvalue for n=10)

[0077] (4) Appearance of each magnet test piece

[0078] (5) The number of magnet test pieces with one or more projectionshaving been produced with the heights exceeding a mean line of roughnesscurves (phase correct filtered mean line) according to JIS B0601-1994 by100 μm or more (the number of defective pieces with projections)(n=500)

[0079] (6) The number of rusted magnet test pieces subjected tocorrosion-resistance test under a condition of being left for 500 hoursunder high-temperature and high-humidity conditions at a temperature of80° C. and a relative humidity of 90% after being subjected to a peeningtreatment with blast material (glass beads manufactured by Sinto BratorLtd. under the trade name GB-AG) injected at a injection pressure of 0.2MPa (the number of rusted defective pieces)(n=10)

[0080] (7) Measurement of adhesion strength by measuring compressionshear strength of magnet test pieces peening treated under the aboveconditions which were bonded to a cast-iron jig with a cyanoacrylateresin adhesive (manufactured by Henkel Japan Ltd. under the trade nameLoctite 406) before being left for 24 hours (averaged value for n=10)

[0081] Measurement of the temperature of the magnet test piecesspecified in (1) was separately carried out, rather than being carriedout simultaneously with deposition of the deposited-films evaluatedaccording to (2) to (7), under the same conditions as those for thedeposition of the deposited-films. Specifically, the following way wasadopted in the measurement. Shavings of a plurality of kinds ofthermocrayons (manufactured by Nichiyu Giken Kogyo Co., Ltd.)representing respective specified temperatures were wrapped with analuminum foil into a package. Such a package was attached around each ofthe magnet test pieces, which were subjected to vapor deposition.Thereafter, it was ascertained how many degrees of temperaturecorrespond to the molten thermocrayon shavings. With respect to theVickers hardness of the aluminum deposited-film at completion of vapordeposition specified in (2), a QM type high temperature microscopichardness tester produced by Japan Optical Co., Ltd. was used as ameasuring apparatus. The hardness was measured under conditions with atest load of 0.5N and a loading time of 30 sec with the magnet testpieces having aluminum deposited-films obtained by the above methodheated up to the temperature at completion of the vapor deposition.Moreover, the number of defective pieces with projections specified in(5) was obtained by observing appearances of the magnet test pieceshaving aluminum deposited-films obtained by the above method under amagnifier (X10). In the observation, when the presence of projectionswere made certain, the height about the highest projection wasdetermined by using a scanning confocal laser microscope (OLS 1100produced by Olympus Optical Co., Ltd.).

[0082] The results are shown in Table 1.

Example 2

[0083] The following experiment was carried out using the vapordeposition apparatus shown in FIG. 2 and FIG. 3. Here, the cylindricalbarrel was made of a stainless steel with 110 mm in diameter by 600 mmin length with 64% in open area ratio of a mesh (with each opening beinga square of 4 mm in side length and with a wire of 1 mm in diameter). Onone support member, there are supported six thereof (in tandem, twelvein total).

[0084] Each of the magnet test pieces was subjected to a shot blasting,whereby an oxide layer on a surface of each of the magnet test pieceswas removed which was produced by a surface working at a preceding step.The magnet test pieces from each of which the oxide layer was removedwere accommodated in twelve cylindrical barrels with 850 pieces foreach, i.e. 20400 pieces in total in two sets in the right and left.After this, an aluminum deposited-film was formed on a surface of eachof the magnet test pieces by an ion plating process for 40 minutes inthe same way as that in the example 1, and evaluated in the same way asthat in the example 1.

[0085] The results are shown in Table 1.

Example 3

[0086] In the example 1, the magnet test pieces, from each of which theoxide layer was removed, were accommodated in two cylindrical barrelswith 5000 pieces for each, i.e. 10000 pieces in total and an aluminumdeposited-film of 10 μm in thickness was formed on the surface of eachof the magnet test pieces by an ion plating process for 20 minutes.Instead of this, here, the magnet test pieces, from each of which theoxide layer was removed, were accommodated in two cylindrical barrelswith 7500 pieces for each, i.e. 15000 pieces in total, an aluminumdeposited-film was formed on a surface of each of the magnet test piecesby an ion plating process for 30 minutes (other conditions were the sameas those in the example 1), and evaluation thereof was carried out inthe same way as that in the example 1.

[0087] The results are shown in Table 1.

Example 4

[0088] In the example 1, the magnet test pieces, from each of which theoxide layer was removed, were accommodated in two cylindrical barrelswith 5000 pieces for each, i.e. 10000 pieces in total and an aluminumdeposited-film of 10 μm in thickness was formed on the surface of eachof the magnet test pieces by an ion plating process for 20 minutes.Instead of this, here, the magnet test pieces, from each of which theoxide layer was removed, were accommodated in two cylindrical barrelswith 10000 pieces for each, i.e. 20000 pieces in total, an aluminumdeposited-film was formed on a surface of each of the magnet test piecesby an ion plating process for 40 minutes (other conditions were the sameas those in the example 1), and evaluation thereof was carried out inthe same way as that in the example 1.

[0089] The results are shown in Table 1.

Comparative Example 1

[0090] In the example 4, an aluminum deposited-film of 10 μm inthickness was formed on a surface of each of the magnet test pieces byan ion plating process for 40 minutes while an aluminum wire wassupplied with a wire feeding speed of 3 g/min. Instead of this, here, analuminum deposited-film was formed on a surface of each of the magnettest pieces by an ion plating process for 80 minutes while an aluminumwire was supplied with a wire feeding speed of 1.5 g/min (otherconditions were the same as those in the example 4), and evaluationthereof was carried out in the same way as that in the example 1.

[0091] The results are shown in Table 1. TABLE 1 Comparative Example 1Example 2 Example 3 Example 4 Example 1 Magnet 280 300 330 365 460temperature (° C.) Vickers 33 30 28 26 15 hardness Film 10.5 9.8 11.010.2 11.0 thickness (μm) Appearance Acceptable Acceptable A few A few Anumber of damages damages damages Number of 0/500 0/500 1/500 8/50078/500 defective pieces with projections Number of 0/10  0/10  0/10 1/10  5/10 rusted defective pieces Adhesion 12.4 13.0 12.0 11.9 3.8(*)strength (MPa)

[0092] As is apparent from Table 1, in example 1 to example 4, bycarrying out the vapor deposition with the temperature of each of themagnet test pieces maintained at ⅔ or less the melting point in bulk(Tm)(°C.) of aluminum, namely, 440° C. or less, the Vickers hardness ofthe film formed on each of the surface of the magnet test pieces couldbe maintained at 25 or more. This can effectively inhibit production ofprojections in the film (for example, presence of projections wasobserved in example 1, but the maximum height thereof was of the orderof 30 μm) to also allow an excellent adhesion strength to be obtainedbetween an adhesive. In addition, damage to the film itself was alsoinhibited to provide the formed film as being excellent in appearanceand in corrosion resistance.

[0093] On the contrary, in comparative example 1, the film was formed bytaking a vapor deposition time twice that in the example 4. Hence, themagnet test pieces were heated more than necessary by the time becominglonger. Thus, the temperature thereof had exceeded 440° C. This made thefilm formed on the surface of each of the magnet test pieces to have aVickers hardness reduced down to 25 or less and to be softened to besusceptible to damage. As a result, a number of projections had beenproduced with the heights thereof exceeding 100 μm. An attempt to bond amagnet test piece with produced projections to a cast-iron jig using anadhesive resulted in insufficient hardening of the adhesive under anormal condition to make it impossible to obtain an excellent adhesionstrength. In addition, the film itself was damaged to be unsatisfactoryin appearance and corrosion resistance.

Example 5

[0094] The following experiment was carried out using the vapordeposition apparatus shown in FIG. 1. In the apparatus, the cylindricalbarrel was made of a stainless steel with 355 mm in diameter by 1200 mmin length with 64% in open area ratio of a mesh (with each opening beinga square of 4 mm in side length and with a wire of 1 mm in diameter).

[0095] Each of the magnet test pieces was subjected to a shot blasting,whereby an oxide layer on a surface of each of the magnet test pieceswas removed which was produced by a surface working at a preceding step.Five thousand magnet test pieces, from each of which the oxide layer wasremoved, were accommodated in one of two cylindrical barrels. After thevacuum-treating chamber was evacuated down to 1×10⁻³ Pa or less, whilerotating the rotary shaft at 1.5 rpm, the magnet test pieces weresubjected to a spattering for 20 minutes under conditions of an argon(Ar) gas pressure of 1 Pa and a bias voltage of −500 V, whereby thesurfaces of the magnet test pieces were cleaned. Subsequently, with azinc ingot used under conditions of an Ar gas pressure of 0.1 Pa as ametal depositing material, a zinc deposited-film was formed on a surfaceof each of the magnet test pieces with a vacuum evaporation process byelectron-beam heating. The vapor deposition was carried out for 1 hourin total while suppressing temperature rise of the magnets by repeatinga heating operation four times. In each of the operation, the heating ofthe ingot was interrupted after 15 minutes had elapsed and restartedafter the ingot had been left for 10 minutes. After being left forcooling, the magnet test pieces having the zinc deposited-film wereevaluated about the following items.

[0096] (1) Temperature of the magnet test pieces at completion of vapordeposition (averaged value for n=10)

[0097] (2) Vickers hardness of the zinc deposited-film at completion ofvapor deposition (averaged value for n=3)

[0098] (3) Thickness of the formed zinc deposited-film (averaged valuefor n=0)

[0099] (4) Appearance of each magnet test piece

[0100] (5) The number of magnet test pieces with one or more projectionshaving been produced with the heights exceeding a mean line of roughnesscurves (phase correct filtered mean line) according to JIS B0601-1994 by100 μm or more (the number of defective pieces with projections)(n=500)

[0101] Measurement of the temperature of the magnet test piecesspecified in (1) was separately carried out, rather than being carriedout simultaneously with deposition of the deposited-films evaluatedaccording to (2) to (5), under the same conditions as those for thedeposition of the deposited-films. Specifically, the following way wasadopted in the measurement. Shavings of a plurality of kinds ofthermocrayons (manufactured by Nichiyu Giken Kogyo Co., Ltd.)representing respective specified temperatures were wrapped with a zincfoil into a package. Such a package was attached around each of themagnet test pieces, which were subjected to vapor deposition.Thereafter, it was ascertained how many degrees of temperaturecorresponds to the molten thermocrayon shavings. The Vickers hardness ofthe zinc deposited-film at completion of vapor deposition specified in(2) was measured in the same way as that described in example 1.Moreover, the number of defective pieces with projections specified in(5) was obtained by making determination in the same way as thatdescribed in example 1.

[0102] The results are shown in Table 2.

Comparative Example 2

[0103] In example 5, without carrying out the operation of heatinginterruption → leaving → heating restarting, the ingot was continuouslyheated for 1 hour for carrying out vapor deposition to form a zincdeposited-film on the surface of each of the magnet test pieces. Thedeposited-films were evaluated in the same way as that in example 5.

[0104] The results are shown in Table 2. TABLE 2 Number of Magnet Filmdefective temperature Vickers thickness pieces with (° C.) hardness (μm)Appearance projections Example 5 240 40 7.3 Acceptable  0/500Comparative 330 21 7.5 A number of 21/500 Example 2 damages

[0105] As is apparent from Table 2, in forming the zinc deposited-filmon the surface of each of the magnet test pieces, by carrying out thevapor deposition with the temperature of each of the magnet test piecesmaintained at ⅔ or less the melting point in bulk (Tm)(°C.) of zinc,namely, 280° C. or less, the Vickers hardness of the film formed on eachof the surface of the magnet test pieces could be maintained at 25 ormore. Thus, no projections were produced in the film and the film itselfwas provided as being excellent in appearance. On the contrary, for thetemperature of the magnet test pieces exceeding 280° C., a number ofprojections had been produced with the heights thereof exceeding 100 μm.In addition, the film itself was damaged to be unsatisfactory inappearance and corrosion resistance.

INDUSTRIAL APPLICABILITY

[0106] According to the present invention, a vapor deposition apparatusis used which comprises, in a vacuum-treating chamber, an evaporatingsection for a depositing material and an accommodating member or aholding member for accommodation or hold of work pieces, respectively,and, in depositing a metal depositing material on each of the surface ofthe work pieces with the accommodating member or the holding memberbeing made rotated about the horizontal rotational axis thereof, vapordeposition is carried out with a Vickers hardness of a film formed oneach of the surface of the work pieces maintained at 25 or more. Thisinhibits the metal deposited-film formed on the surface of each of thework pieces from being softened to become damageable by collisions andrubbings of the work pieces against one another and by collisions andrubbings between the work pieces and the barrel wall. As a result,production of projections in the film can be effectively inhibited.

[0107] In forming a metal deposited-film on the surface of each of thework pieces before continuously forming on the surface a film of ceramicsuch as Al₂O₃ or TiN, projections having been produced in the metaldeposited-film have effect on a subsequently formed ceramic film aboutadhesion reliability with an adhesive and dimensional accuracy.According to the present invention, however, such adverse effects can bealso avoided.

1. A method of inhibiting production of projections in a metaldeposited-film characterized by using a vapor deposition apparatuscomprising, in a vacuum-treating chamber, an evaporating section for adepositing material, and an accommodating member and/or a holding memberfor accommodation and/or hold of work pieces, respectively, and, indepositing a metal depositing material on each of the surface of saidwork pieces with said accommodating member and/or said holding memberbeing made rotated about the horizontal rotational axis thereof,carrying out vapor deposition with a Vickers hardness of a film formedon each of the surface of said work pieces maintained at 25 or more. 2.A method according to claim 1 characterized in that a temperature ofeach of said work pieces accommodated and/or held in said accommodatingmember and/or said holding member, respectively, is maintained at ⅔ orless a melting point in bulk (Tm)(°C.) of said metal depositing materialto thereby maintain the Vickers hardness of said film formed on each ofthe surface of said work pieces at 25 or more.
 3. A method according toclaim 2 characterized in that said metal depositing material isaluminum, with which vapor deposition is carried out with a temperatureof said work piece maintained at 350° C. or less.
 4. A method accordingto claim 2 characterized in that said metal depositing material is zinc,with which vapor deposition is carried out with a temperature of saidwork piece maintained at 250° C. or less.
 5. A method according to anyone of claim 1 to claim 4 characterized in that the vapor deposition iscarried out by a vacuum evaporation process or an ion plating process.6. A method according to any one of claim 1 to claim 5 characterized inthat said accommodating member and/or said holding member are/isdetachably constituted.
 7. A method according to any one of claim 1 toclaim 6 characterized in that said accommodating member is a tubularbarrel formed of a mesh net.
 8. A method according to claim 7characterized in that said tubular barrel is revolvably supportedcircumferentially outside a horizontal rotational axis of a supportmember made rotatable about the rotational axis, for revolution aboutthe rotational axis of said support member by rotating said supportmember.
 9. A method according to claim 8 characterized in that saidtubular barrel and/or said support member supporting said tubular barrelare/is detachably constituted.
 10. A method according to claim 8characterized in that a plurality of said tubular barrels are supportedin an annular shape circumferentially outside the rotational axis ofsaid support member.
 11. A method according to claim 7 characterized inthat the inside of said tubular barrel is divided to form two or moreaccommodating sections.
 12. A method according to claim 11 characterizedin that the inside of said tubular barrel is divided radially from arotational axis to form two or more accommodating sections.
 13. A methodaccording to any one of claim 1 to claim 12 characterized in that saidwork piece is a rare earth metal-based permanent magnet.
 14. A rareearth metal-based permanent magnet characterized by having a metaldeposited-film in which production of projections is inhibited by themethod according to claim
 13. 15. A rare earth metal-based permanentmagnet according to claim 14 characterized in that a height of theprojection exists in said metal deposited-film is above a mean line ofroughness curves (phase correct filtered mean line) according to JISB0601-1994 by 100 μm or less.